The majority of present day integrated circuits are implemented by using a plurality of interconnected field effect transistors (FETs), also called metal oxide semiconductor field effect transistors (MOSFETs), or simply MOS transistors. Such semiconductor devices are used in many electronic and other applications. Semiconductor devices include integrated circuits that are formed on semiconductor wafers by depositing many types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits.
One such application of semiconductor devices is in cell phones and laptop computers, which are playing important roles in our everyday lives, and the demand for more portable electronic devices continues to increase rapidly. This growing demand is currently driving the integration or embedding of passive components in semiconductor devices, which would replace off-chip discrete modular assemblies. Meanwhile, various approaches of integration in system-on-a-chip (SoC) and system-in-package (SiP) circuits are gaining much attention. However, the poor properties of integrated inductors have been a critical factor limiting the overall performance of radio-frequency (RF) circuits and hence the realization of RF SoC or SiP circuits.
Inductors are passive devices that are widely used in many applications. Integrated inductors are usually formed using conventional semiconductor fabrication processes. While improvements in performance of inductors are constantly sought, there is also a demand in semiconductor device technology to integrate many different functions on a single chip, e.g., manufacturing various types of active and passive devices on the same die. However, such integration creates additional challenges that need to be overcome. For example, conventional inductive structures require large surface areas or have limited performance. For aggressive integration, it is essential to have a low surface area along with a high quality factor.
The use of a magnetic core with high permeability in the integrated inductor has been proposed in the prior art to significantly increase the inductance by the relative permeability of the magnetic material used. This, in turn, can significantly reduce the device area and the coil resistance needed to meet the inductance requirement. However, prior art magnetic core inductors still suffer from several technical challenges. For example, in U.S. Pat. No. 7,262,680 B2 to Albert H. Wang, it was proposed to use an on-chip inductor device for integrated circuits that utilizes coils on a plurality of metal layers of the integrated circuit with electrical connectors between the coils and a magnetic core for the inductor of stacked vias running between the coils. This structure, however, may be found to suffer from a relatively low inductance density, along with the possibility of electromagnetic interference because the magnetic field generated by the inductor could penetrate through the semiconductor substrate underneath. As a further example, in Lee et al., IEEE TRANSACTIONS ON MAGNETICS, Vol. 44, No. 11, P. 4089 (November 2008), the authors proposed integrated inductors using a solenoid design with a single magnetic layer. This structure, however, like the one proposed by Wang, may suffer from a relatively low inductance density, and has not found wide application in portable electronic devices.
Therefore, it will become apparent to those skilled in the art that there remains a present and continuing need for the provision of improved integrated inductor structures for use in SoC and SiC circuits. The inductor structures would desirably exhibit a relatively high inductance density in addition to having protection against electromagnetic interference due to the magnetic field generated. It would be desirable for such structures to be easily fabricated using existing semiconductor fabrication processes, such as conventional back-end-of-line (BEOL) processing techniques. Still further, other desirable features and characteristics of the subject matter will become apparent from the subsequent detailed description of the subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.